Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

ID 814346
Date 7/19/2024
Public
Document Table of Contents

5.4.9.1. SD Card Level Shifting

HPS I/O only supports 1.8V signaling. Most SD cards require 3.3V operation at initial power-up time, and they typically require switching to 1.8V after initialization time to support higher speed operation.

To support 3.3V operation, a level shifter is required. Level shifters are available on the market, designed specifically for this purpose.

There are also LVS SD cards that only support 1.8V operation, and the controller could communicate with those cards without the need of level shifters. To properly detect and initialize LVS SD cards, you need to use the PU_PD_DAT2 signal to control the pull up or down of the DAT2 signal.

Refer to SD Voltage Switching for more details.